Application of Porous Phosphate Heterostructure Materials for Gas Separation

In this study, the adsorbents Cu+−3SiPPH723 and Cu2+−3SiPPH723 were prepared starting from a silica-expanded zirconium phosphate heterostructure, 3SiPPH(0.2), which was subjected to an ion exchange with Cu(I) and Cu(II). These materials were characterized using powder X-ray diffraction, X-ray photoelectron spectroscopy, ammonia thermally programmed desorption, hydrogen temperature-programmed reduction, and N2 adsorption (77 K). The equilibria and kinetics of adsorption of pure propylene (C3H6) and propane (C3H8) were studied using a conventional glass high-vacuum volumetric device, equipped with grease-free valves, in the temperature range of 273−393 K. The starting material, 3SiPPH(0.2), presented a high acidity and irreversible chemisorption of the olefin, which increases with temperature. Unlike the support, the irreversible adsorption of the olefin on the Cu+−3SiPPH723 and Cu2+−3SiPPH723 samples decreases with increasing temperature and disappears at 393 K, showing a very high selectivity toward propylene. The C3H8 adsorption in all the samples was always reversible. On the basis of the results of this study, both Cu+−3SiPPH723 and Cu2+−3SiPPH723 samples can be efficiently applied in the separation of a C3H6/C3H8 mixture at 393 K. Cu+−3SiPPH723 would have the highest efficiency, because its capacity for C3H6 adsorption was higher than that for the Cu2+−3SiPPH723 sample.